The fireplace has served as the principal source of heat for the household prior to the 20th century. However, fireplaces heretofore have heated principally by radiative heating and over 80% of the heat value of the fuel combusted therein is wasted in the form of cumbustion gases which are conducted out of the throat of the firebox before their heat content can be usefully extracted. The 20th century has seen the fireplace, as an effective heating means, cast aside in favor of more efficient centralized heating systems burning fuels such as natural gas, oil, coal or electricity. Although the operational fireplace has been retained in the design of many homes being built today, it serves principally as an ornament, being only occasionally used.
However, with the onset of a world wide scarcity in the fuels used in centralized heating systems, the public interest is renewed in making use of the fireplace as a functional element in the heating of the home. New designs are now being sought to improve the efficiency of the fireplace as a heating plant.
In its long history of existence, many improvements have been attempted to increase the heating efficiency of the fireplace. For example, cumbersome superstructures have been developed which employ air convection principles to circulate air about the firebox and back into the ambient. These prior art structures are characterized by their inefficient extraction of heat from the firebox due principally to the interception of the radiant heat in the back and sides of the firebox. Other approaches to improving the efficiency of the conventional fireplace include the use of a small, roll-about heat exchanger assembly which can be rolled into the firebox and attached to a source of forced air. This type of heat exchanger apparatus fails to optimumly extract heat from the combustion gases since it does not take advantage of the substantial amount of heat conducted through the throat and up the flue.
Another problem with the fireplace in the prior art, which has been generally ignored, is that the equipment of the fireplace generally lies idle during the spring, summer and fall months, only being brought into use during the winter when heating is required. Centralized cooling systems used in the warmer months are generally expensive, specialized units being totally unrelated to the idle fireplace equipment.